Conventional urinals and toilets have a waste outlet into which urine, feces and the like passes.
Sanitation codes require the discharge conduit from a urinal be provided with a trap to contain gases which develop in the drain system. Typically, the trap is an S-shaped trap in which a residual portion of fluid fills an upwardly opening U-shaped segment of the trap providing a barrier to sewer gases and odors passing from below the trap upwardly. The upwardly facing liquid surface in the trap freely communicates via the urinal outlet with air in the washroom. Many urinals have the disadvantage that to keep liquid in the trap free of residue urine requires copious flushing with water after each use.
Conservation desires have increased the need for a reduction of water usage in flushing urinals and toilets with a view to reduce water consumption and to also reduce waste water disposal requirements. Low flush toilets are also known to be provided with an S-trap with a small diameter such that a smaller volume of flushing liquid is required in order to provide clean liquid in the trap.
Waterless or low flush urinals are also known in which a layer of oil which has a lower density than water is used in the trap to act as the odor seal. Oil-sealed odor traps suffer the disadvantage that some of the urine typically remains in the oil resulting in odors passing into a washroom area. Insofar as the oil may have disinfectant properties, the oil typically disadvantageously requires frequent cleaning and replacement, sometimes daily.